Isolated converter

ABSTRACT

An isolated converter reduced in size compared with a conventional isolated converter and having a high heat dissipation characteristic is provided. The isolated converter includes a multilayer substrate having a first through hole and a magnetic core partially passing through the first through hole. The multilayer substrate includes a first conductor pattern formed at a position overlapping the magnetic core on a second surface when viewed from a direction orthogonal to a first surface, a second conductor pattern formed between the first surface and the second surface at a position overlapping the magnetic core and the first conductor pattern when viewed from the direction orthogonal to the first surface, at least one thermal conductive member formed on the first conductor pattern and having a portion disposed between the multilayer substrate and the magnetic core, and an electric insulating layer electrically insulating the first conductor pattern from the second conductor pattern.

TECHNICAL FIELD

The present invention relates to an isolated converter and morespecifically to an isolated converter including a transformer havingcoils formed with patterns formed on a multilayer substrate.

BACKGROUND ART

Isolated converters having primary-side and secondary-side coils formedon multilayer substrates have been known. In a conventional isolatedconverter, a primary-side coil and a secondary-side coil are formed withwinding patterns separated from each other by an isolation distance on afront layer and an internal layer of a multilayer substrate.

Magnetic devices including choke coils formed on multilayer substratesalso have been known. Japanese Patent Laying-Open No. 2014-199908(PTL 1) discloses a magnetic device in which coils are formed with aplurality of coil patterns formed on an exterior layer and an internallayer of a multilayer substrate. In the magnetic device described in PTL1 above, a heat dissipation pin electrically continuous with a coilpattern on the internal layer and a heat dissipation pin electricallyinsulated are formed, and the heat dissipation pins are connected to aheat sink on the exterior layer.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laying-Open No. 2014-199908

SUMMARY OF INVENTION Technical Problem

However, in the conventional isolated converter, a predeterminedisolation distance need to be provided even between a heat conductionvia connecting the primary-side coil with the cooler and a heatconduction via connecting the secondary-side coil with the cooler. Inorder to provide an isolation distance in this manner, for example, aheat conduction via may be formed at a sufficient distance from the coilpattern. However, in this case, the size of the isolated converter isincreased. Moreover, the distance between the heat generation portionand the heat conduction via is long, which makes it difficult tosufficiently dissipate the heat from the heat generation portion.

Moreover, for example, if the size (for example, width) of the coilpattern is reduced in order to provide an isolation distance between thecoil pattern and the heat conduction via, the amount of heat generationin the coil pattern is increased. In the magnetic device described inPTL 1 above, heat is unable to be dissipated sufficiently through theheat dissipation pin when the distance between the heat generationportion and the heat dissipation pin is long.

The present invention is made in order to solve the problem as describedabove. The main object of the present invention is to provide anisolated converter reduced in size compared with a conventional isolatedconverter and having a high heat dissipation characteristic.

Solution to Problem

An isolated converter according to the present invention includes asubstrate having a first surface and a second surface positioned on aside opposite to the first surface and having a first through holeextending from the first surface to the second surface, and a magneticcore partially passing through the first through hole. The substrateincludes a first conductor pattern formed at a position overlapping themagnetic core on the second surface when viewed from an orthogonaldirection to the first surface, a second conductor pattern formedbetween the first surface and the second surface at a positionoverlapping the magnetic core and the first conductor pattern whenviewed from the orthogonal direction to the first surface, at least onethermal conductive member formed on the first conductor pattern andhaving a portion disposed between the substrate and the magnetic core,and an insulative heat-transferring member electrically insulating thefirst conductor pattern from the second conductor pattern.

Advantageous Effects of Invention

The present invention provides an isolated converter reduced in sizecompared with a conventional isolated converter and having a high heatdissipation characteristic.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an isolated converter according toa first embodiment.

FIG. 2 is an exploded perspective view showing a transformer part of theisolated converter according to the first embodiment.

FIG. 3 is a cross-sectional view of a multilayer substrate forming thetransformer part of the isolated converter according to the firstembodiment.

FIG. 4 is a circuit diagram of the isolated converter according to thefirst embodiment.

FIGS. 5(A)-(D) are plan views of the layers of the multilayer substrateshown in FIG. 3 when viewed from the first surface side, in which (A) isa plan view of a first layer, (B) is a plan view of a second layer, (C)is a plan view of a third layer, and (D) is a plan view of a fourthlayer.

FIG. 6(A) is a cross-sectional view taken along line VI(A)-VI(A) shownin FIG. 5(A), FIG. 6(B) is a cross-sectional view taken along lineVI(B)-VI(B) shown in FIG. 5(B), FIG. 6(C) is a cross-sectional viewtaken along line VI(C)-VI(C) shown in FIG. 5(C), and FIG. 6(D) is across-sectional view taken along line VI(D)-VI(D) shown in FIG. 5(D).

FIGS. 7(A) and 7(B) are plan views showing a modification of the thermalconductive member in the isolated converter according to the firstembodiment.

FIG. 8(A) is a plan view showing another modification of the thermalconductive member in the isolated converter according to the firstembodiment, and FIG. 8(B) is a cross-sectional view taken along lineVIII(B)-VIII(B) in FIG. 8(A).

FIG. 9 is a plan view showing a modification of the fourth conductorpattern in the isolated converter according to the first embodiment.

FIG. 10 is a circuit diagram of an isolated converter according to asecond embodiment.

FIGS. 11(A)-(D) are plan views of the layers of the multilayer substratein the isolated converter according to the second embodiment when viewedfrom the first surface side, in which (A) is a plan view of a firstlayer, (B) is a plan view of a second layer, (C) is a plan view of athird layer, and (D) is a plan view of a fourth layer.

FIG. 12(A) is a cross-sectional view taken along line XII(A)-XII(A)shown in FIG. 11(A), FIG. 12(B) is a cross-sectional view taken alongline XII(B)-XII(B) shown in FIG. 11(B), FIG. 12(C) is a cross-sectionalview taken along line XII(C)-XII(C) shown in FIG. 11(C), and FIG. 12(D)is a cross-sectional view taken along line XII(D)-XII(D) shown in FIG.11(D).

FIG. 13 is a circuit diagram of an isolated converter according to athird embodiment.

FIGS. 14(A)-(D) are plan views of the layers of the multilayer substratewhen viewed from the first surface side in the isolated converteraccording to the third embodiment, in which (A) is a plan view of afirst layer, (B) is a plan view of a second layer, (C) is a plan view ofa third layer, and (D) is a plan view of a fourth layer.

FIG. 15(A) is a cross-sectional view taken along line XV(A)-XV(A) shownin FIG. 14(A), FIG. 15(B) is a cross-sectional view taken along lineXV(B)-XV(B) shown in FIG. 14(B), FIG. 15(C) is a cross-sectional viewtaken along line XV(C)-XV(C) shown in FIG. 14(C), and FIG. 15(D) is across-sectional view taken along line XV(D)-XV(D) shown in FIG. 14(D).

FIGS. 16(A)-(D) are plan views of the layers of the multilayer substratewhen viewed from the first surface side in an isolated converteraccording to a fourth embodiment, in which (A) is a plan view of a firstlayer, (B) is a plan view of a second layer, (C) is a plan view of athird layer, and (D) is a plan view of a fourth layer.

FIG. 17 is a circuit diagram of an isolated converter according to afifth embodiment.

FIGS. 18(A)-(D) are plan views of the layers of the multilayer substratewhen viewed from the first surface side in the isolated converteraccording to the fifth embodiment, in which (A) is a plan view of afirst layer, (B) is a plan view of a second layer, (C) is a plan view ofa third layer, and (D) is a plan view of a fourth layer.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below withreference to the figures. In the figures described below, the same orcorresponding parts are denoted by the same reference numerals and adescription thereof will not be repeated.

First Embodiment

<Configuration of Isolated Converter>

Referring to FIG. 1 to FIG. 3, a configuration of an isolated converter100 according to a first embodiment will be described. Isolatedconverter 100 includes a transformer 1, a primary-side drive circuit 2,a rectifying circuit 3, and a smoothing circuit 4. Transformer 1,primary-side drive circuit 2, rectifying circuit 3, and smoothingcircuit 4 are mounted on a multilayer substrate 8.

Transformer 1 includes a primary-side coil 11A (see FIG. 4) andsecondary-side coils 12A, 12B configured with conductor patterns formedon multilayer substrate 8, and magnetic cores 13, 14 (see FIG. 2). Thedetailed configuration of transformer 1 will be described later.Primary-side drive circuit 2 includes a plurality of switching elements21A, 21B, 21C, 21D mounted on multilayer substrate 8. Rectifying circuit3 includes a plurality of rectifying elements 31A, 31B (see FIG. 4)mounted on multilayer substrate 8. Smoothing circuit 4 includes asmoothing capacitor 41, a smoothing coil 42 configured with a conductorpattern formed on multilayer substrate 8, and a magnetic core 43.Multilayer substrate 8 has a first surface 8A and a second surface 8Dpositioned on the opposite side to first surface 8A. Second surface 8Dof multilayer substrate 8 is connected and fixed to a casing 71(cooler).

As shown in FIG. 4, primary-side drive circuit 2 is configured with aswitching element 21A and a switching element 21B connected in seriesand a switching element 21C and a switching element 21D connected inseries. Primary-side coil 11A of transformer 1 is connected between acontact point 22 between switching element 21A and switching element 21Band a contact point 23 between switching element 21C and switchingelement 21D. Switching element 21A and switching elements 21B, 21C, 21Dare, for example, MOSFETs. The drain terminals of switching elements21A, 21C are connected to the positive side of a direct-current (DC)power supply 6. The source terminals of switching elements 21B, 21D areconnected to the negative side of DC power supply 6.

In rectifying circuit 3, the cathode terminals of rectifying elements31A, 31B are connected to secondary-side coils 12A, 12B of transformer1. The anode terminals of rectifying elements 31A, 31B are connected toa reference potential 7 on the secondary side of isolated converter 100.A contact point 34 between secondary-side coils 12A and 12B is connectedto smoothing coil 42 in smoothing circuit 4. Smoothing coil 42 andsmoothing capacitor 41 are connected in series. Voltage Vo of smoothingcapacitor 41 in smoothing circuit 4 serves as output voltage(secondary-side voltage) Vo of isolated converter 100.

Primary-side drive circuit 2 and smoothing circuit 4 are connected to acontrol circuit 5. Control circuit 5 controls the on/off operation ofswitching elements 21A, 21B, 21C, 21D in primary-side drive circuit 2such that voltage Vo of smoothing capacitor 41 has a predeterminedvalue.

<Configuration of Transformer>

Referring now to FIG. 2 to FIG. 6, a specific configuration oftransformer 1 will be described. Magnetic cores 13, 14 of transformer 1are, for example, an E-shaped core 13 having an E-shaped side surfaceand an I-shaped core 14 having an I-shaped side surface. E-shaped core13 has outside legs 13A, 13B and an inside leg 13C. In a region havingtransformer 1 on multilayer substrate 8, through holes 84A, 84B, 84C areformed to extend from first surface 8A to second surface 8D. Outsidelegs 13A, 13B and inside leg 13C of E-shaped core 13 are inserted inthrough holes 84A, 84B, 84C, respectively. A coupling portion couplingoutside legs 13A, 13B and inside leg 13C of E-shaped core 13 is disposedon, for example, first surface 8A of multilayer substrate 8. I-shapedcore 14 is disposed on, for example, second surface 8D of multilayersubstrate 8 and connected to outside legs 13A, 13B and inside leg 13C ofE-shaped core 13. Thus, in magnetic cores 13, 14, a magnetic pathpassing through outside leg 13A and inside leg 13C and a magnetic pathpassing through outside leg 13B and inside leg 13C are formed.

As shown in FIG. 3, multilayer substrate 8 is configured as, forexample, a stack structure in which four conductor pattern layers 81A,81B, 81C, 81D and three electric insulating layers 82A, 82B, 82C arealternately stacked in a direction orthogonal to first surface 8A(hereinafter simply referred to as orthogonal direction). Conductorpattern layer 81A is formed on first surface 8A. Conductor pattern layer81D is formed on second surface 8D. Conductor pattern layer 81B isformed between first surface 8A and second surface 8D and is stackedwith conductor pattern layer 81A with electric insulating layer 82Ainterposed therebetween. Conductor pattern layer 81C is formed betweenfirst surface 8A and second surface 8D and is stacked with conductorpattern layer 81B with electric insulating layer 82C interposed.Conductor pattern layer 81B is stacked with conductor pattern layer 81Cwith electric insulating layer 82B interposed. In other words, conductorpattern layer 81A, electric insulating layer 82A, conductor patternlayer 81B, electric insulating layer 82B, conductor pattern layer 81C,electric insulating layer 82C, and conductor pattern layer 81D arestacked in this order.

The material forming conductor pattern layers 81A, 81B, 81C, 81D is anymaterial that has electric conductivity, and examples include copper(Cu). The material forming electric insulating layers 82A, 82B, 82C isany material that has electrical insulating properties and is preferablya material having a relatively high thermal conductivity. That is,electric insulating layers 82A to 82C are configured as members havingelectrical insulating properties and having a high thermal conductivity(insulative heat-transferring member).

Conductor pattern layers 81A to 81D each have a thickness of, forexample, 35 pm to 105 pm. The thickness of electric insulating layer82A, 82C in the orthogonal direction is thinner than the thickness ofelectric insulating layer 82B and, for example, 0.1 mm to 0.3 mm. Thethickness of electric insulating layer 82B is, for example, 0.6 mm to1.0 mm. Electric insulating layer 82A provides electrical insulation andthermal connection between conductor pattern layer 81A and conductorpattern layer 81B. Electric insulating layer 82B provides electricalinsulation and thermal connection between conductor pattern layer 81Band conductor pattern layer 81C. Electric insulating layer 82C provideselectrical insulation and thermal connection between conductor patternlayer 81C and conductor pattern layer 81D.

As shown in FIG. 5, each of conductor pattern layers 81A, 81B, 81C, 81Dhas a conductor pattern forming primary-side coil 11A or secondary-sidecoils 12A, 12B and another conductor pattern formed on the periphery ofthe conductor pattern. The conductor patterns of conductor patternlayers 81A, 81B, 81C, 81D are electrically connected through vias 81E to81J to form an electrical circuit shown in FIG. 2 on multilayersubstrate 8 (detail will be described later).

As shown in FIG. 5(A), conductor pattern layer 81A has a third conductorpattern 85A forming secondary-side coil 12A and conductor patterns 86A,87A formed on the periphery of third conductor pattern 85A. Thirdconductor pattern 85A is formed in the form of winding so as to surroundthrough hole 84C. Third conductor pattern 85A has a portion formedbetween through hole 84C and through hole 84A and a portion formedbetween through hole 84C and through hole 84B. Conductor patterns 86A,87A are formed at a distance from third conductor pattern 85A.

As shown in FIG. 5(B), conductor pattern layer 81B has a fourthconductor pattern 85B forming primary-side coil 11A, and a conductorpattern 86B (sixth conductor pattern) and a conductor pattern 87B formedon the periphery of fourth conductor pattern 85B. Fourth conductorpattern 85B is formed in the form of winding so as to surround throughhole 84C. Conductor patterns 86B, 87B, 88B are formed at an isolationdistance from fourth conductor pattern 85B.

As shown in FIG. 5(C), conductor pattern layer 81C has a secondconductor pattern 85C forming primary-side coil 11A, and a conductorpattern 86C (sixth conductor pattern) and a conductor pattern 87C formedon the periphery of second conductor pattern 85C. Second conductorpattern 85C is formed in the form of winding so as to surround throughhole 84C. Conductor patterns 86C, 87C, 88C are formed at an isolationdistance from second conductor pattern 85C.

As shown in FIG. 5(D), conductor pattern layer 81D has a first conductorpattern 85D forming secondary-side coil 12B, and a conductor pattern 86D(fifth conductor pattern) and a conductor pattern 87D formed on theperiphery of first conductor pattern 85D. First conductor pattern 85D isformed in the form of winding so as to surround through hole 84C. Firstconductor pattern 85D has a portion formed between through hole 84C andthrough hole 84A and a portion formed between through hole 84C andthrough hole 84B. Conductor patterns 86D, 87D are formed at a distancefrom first conductor pattern 85D.

As shown in FIGS. 5(A) to 5(D), fourth conductor pattern 85B is formedsuch that, when viewed from the orthogonal direction (when first surface8A is viewed two-dimensionally), a large part (for example, an arearatio of 80% or more, preferably 90% or more) of the positionoverlapping the coupling portion of the E-shaped core overlaps conductorpattern layer 81A, for example, third conductor pattern 85A. Secondconductor pattern 85C is formed such that, when viewed from theorthogonal direction to first surface 8A (when first surface 8A isviewed two-dimensionally), a large part (for example, an area ratio of80% or more, preferably 90% or more) of the position overlapping thecoupling portion of the E-shaped core overlaps conductor pattern layer81D, for example, first conductor pattern 85D.

As shown in FIG. 5(A), thermal conductive members 91A, 91B, 91C areformed on third conductor pattern 85A. Each of thermal conductivemembers 91B, 91C is formed so as to be positioned between magnetic core13 and multilayer substrate 8. Each of thermal conductive members 91A,91B, 91C is formed so as to surround through hole 84C. It is preferablethat each of thermal conductive members 91A, 91B, 91C has a portionformed on a region overlapping fourth conductor pattern 85B in thirdconductor pattern 85A when viewed from the orthogonal direction. Each ofthermal conductive members 91A, 91B, 91C is formed, for example, alongone side of through hole 84C. Thermal conductive member 91A and thermalconductive member 91B may be formed, for example, at a distance (gapportion) from each other. Thermal conductive member 91A and thermalconductive member 91C may be formed, for example, at a distance fromeach other.

As shown in FIG. 5(D), thermal conductive members 91D, 91E, 91F areformed on first conductor pattern 85D. Each of thermal conductivemembers 91E, 91F is formed so as to be positioned between magnetic core14 and multilayer substrate 8. Each of thermal conductive members 91D to91F is formed so as to surround through hole 84C. It is preferable thateach of thermal conductive members 91D to 91F has a portion formed on aregion overlapping second conductor pattern 85C in first conductorpattern 85D when viewed from the orthogonal direction. Each of thermalconductive members 91D to 91F is formed, for example, along one side ofthrough hole 84C. Thermal conductive member 91D and thermal conductivemember 91E may be formed, for example, at a distance from each other.Thermal conductive member 91D and thermal conductive member 91F areformed, for example, at a distance from each other. Thermal conductivemembers 91A to 91F may have any shape, for example, a rectangulartwo-dimensional shape. Three thermal conductive members 91A to 91Cformed on third conductor pattern 85A and three thermal conductivemembers 91D to 91F formed on first conductor pattern 85D are formed, forexample, in a C shape when viewed from the orthogonal direction.

As shown in FIGS. 5(A) and 5(D), thermal conductive member 91A formed onthird conductor pattern 85A and thermal conductive member 91D formed onfirst conductor pattern 85D are formed so as to overlap each other, forexample, when viewed from the orthogonal direction. Similarly, thermalconductive member 91B and thermal conductive member 91E as well asthermal conductive member 91C and thermal conductive member 91F areformed so as to overlap each other, for example, when viewed from theorthogonal direction. The gap portion between thermal conductive member91A and thermal conductive member 91B is formed so as to overlap the gapportion between thermal conductive member 91D and thermal conductivemember 91E, and the gap portion between thermal conductive member 91Aand thermal conductive member 91C is formed so as to overlap the gapportion between thermal conductive member 91D and thermal conductivemember 91F, for example, when viewed from the orthogonal direction.

The material forming thermal conductive members 91A to 91F may be anymaterial having a relatively high thermal conductivity and, for example,includes a material having a thermal conductivity equal to or higherthan the material forming conductor pattern layers 81A to 81D, forexample, including Cu or Cu alloy. Thermal conductive members 91A to 91Fhave a thickness of, for example, 0.5 mm to 1.0 mm. Thermal conductivemembers 91A to 91F are bonded on third conductor pattern 85A and firstconductor pattern 85D with a material having a high thermalconductivity, for example, such as solder. It is preferable that thermalconductive members 91A to 91F are bonded entirely with third conductorpattern 85A and first conductor pattern 85D disposed entirely below.

As shown in FIGS. 5(A) to 5(D) and FIGS. 6(A) and 6(B), multilayersubstrate 8 has a plurality of vias 81E, 81G, 81H, 81I, 81J electricallyconnecting conductor pattern layers 81A, 81B, 81C, 81D. The materialforming vias 81E to 81J may be any material having electricalconductivity and includes, for example, Cu. Vias 81E to 81J may beformed, for example, by plating through holes on electric insulatinglayers 82A to 82C with copper. Vias 81E to vias 81J are formed onconductor pattern layers 81A to 81D in a distributed manner in adirection along first surface 8A.

Via 81E is connected to one end of third conductor pattern 85A,conductor patterns 88B, 88C, and one end of first conductor pattern 85D.Via 81G is formed such that thermal conductive member 91B is positionedbetween the portion connected to via 81G and the portion connected tovia 81E in third conductor pattern 85A. Via 81H is formed such thatthermal conductive member 91A is positioned between the portionconnected to via 81H and the portion connected to via 81G in thirdconductor pattern 85A. Via 81I is formed such that thermal conductivemember 91C is positioned between the portion connected to via 81I andthe portion connected to via 81H in third conductor pattern 85A.Furthermore, each of vias 81G, 81H, 81I is connected to conductorpatterns 86B, 86C, 86D. Via 81J is connected to conductor pattern 86A.Via 81J is connected to the other end of first conductor pattern 85D.

Multilayer substrate 8 further includes a via 81F electricallyconnecting only between conductor pattern layer 81B and conductorpattern layer 81C. Via 81F may be formed in electric insulating layers82A and 82C so as to extend from conductor pattern layer 81B to firstsurface 8A or extend from conductor pattern layer 81C to second surface8D. In this case, via 81F is formed at an isolation distance fromconductor pattern layer 81A and conductor pattern layer 81D and isformed so as not to be electrically connected thereto. As shown in FIGS.6(C) and 6(D), multilayer substrate 8 has fixing holes 73A, 73B forreceiving fixtures 74A, 74B for fixing multilayer substrate 8 to casing71. Fixing holes 73A, 73B are formed so as to extend from first surface8A to second surface 8D and pass through conductor pattern layers 81A to81D. On the inner circumferential surfaces of fixing holes 73A, 73B, aconductive film of a material having electrical conductivity, forexample, a Cu film may be formed. The conductive film may be formed, forexample, by plating.

Multilayer substrate 8 exhibiting the configuration as described aboveis connected and fixed to casing 71 on the second surface 8D side. Eachof first conductor pattern 85D and fifth conductor pattern 86D formed onsecond surface 8D is connected to casing 71 with a heat dissipationsheet 72 interposed. Conductor pattern 87D formed on second surface 8Dis directly connected to casing 71. The material forming heatdissipation sheet 72 is a material having electrical insulatingproperties and having a relatively high thermal conductivity (forexample, a material having a thermal conductivity equal to or higherthan 1.0 W/mK). As heat dissipation sheet 72, for example, a thermalinterface silicone ultra soft pad TC-CAS-10 (thermal conductivity of 1.8W/mK) manufactured by Shin-Etsu Chemical Co., Ltd. or a thermalconductive spacer FSL-J (thermal conductivity of 1.0 W/mK) manufacturedby Denka Company Limited may be employed.

Referring now to FIG. 2, FIG. 5 and FIG. 6, an electric circuit,specifically, the circuits related to transformer 1 formed on multilayersubstrate 8 will be described. Referring to FIG. 2 and FIGS. 5(B) and5(C), one end of fourth conductor pattern 85B is connected to one end ofsecond conductor pattern 85C through via 81F. The other end of fourthconductor pattern 85B is connected to contact point 22 of primary-sidedrive circuit 2. The other end of second conductor pattern 85C isconnected to contact point 23 of primary-side drive circuit 2. Thus,fourth conductor pattern 85B and second conductor pattern 85C areconnected in series with contact points 22, 23 to form primary-side coil11A.

Referring to FIG. 2, FIGS. 5(A) and 5(D), and FIGS. 6(A) and 6(B), oneend of third conductor pattern 85A is connected to the cathode terminalof rectifying element 31A. One end of first conductor pattern 85D isconnected to the cathode terminal of rectifying element 31B throughconductor pattern 86A and via 81J. The other end of third conductorpattern 85A and the other end of first conductor pattern 85D areconnected through via 81E and are connected to conductor pattern 88B andconductor pattern 88C through via 81E. Conductor patterns 88B, 88C areconnected to contact point 34 of smoothing circuit 4. Thus, thirdconductor pattern 85A and first conductor pattern 85D are connected inparallel with contact point 34 and form secondary-side coil 12A andsecondary-side coil 12B. The anode terminals of rectifying elements 31A,31B are connected to casing 71 serving as reference potential 7 throughconductor pattern 87A, fixing holes 73A, 73B, and conductor pattern 87D.

In multilayer substrate 8, the primary-side circuit and thesecondary-side circuit of transformer 1 are formed on conductor patternlayer 81B and conductor pattern layer 81C. Specifically, fourthconductor pattern 85B and second conductor pattern 85C are connected toprimary-side drive circuit 2. Conductor patterns 86B, 87B, 88B andconductor patterns 86C, 87C, 88C are connected to the secondary-sidecircuit such as rectifying circuit 3 and smoothing circuit 4. On theother hand, only the secondary-side circuit of transformer 1 is formedon conductor pattern layer 81A and conductor pattern layer 81D, exceptvia 81F. Specifically, third conductor pattern 85A, conductor pattern86A, conductor pattern 87A, first conductor pattern 85D, fifth conductorpattern 86D, and conductor pattern 87D are connected to thesecondary-side circuit such as rectifying circuit 3 and smoothingcircuit 4. In multilayer substrate 8, the conductor pattern forming theprimary-side circuit and the conductor pattern forming thesecondary-side circuit are formed to be spaced apart by at least anisolation distance that can satisfy a dielectric voltage (for example, 2kV/min) required for isolated converter 100. As for the isolationdistance, the isolation distance in conductor pattern layers 81B, 81Cembedded in electric insulating layers 82A to 82C is shorter than theisolation distance in conductor pattern layers 81A, 81D not embedded inan electric insulating layer.

Referring now to FIG. 5 and FIG. 6, heat dissipation paths formed inmultilayer substrate 8, specifically heat dissipation paths fortransformer 1 will be described. In FIGS. 6(A) to 6(D), some of the heatdissipation paths are illustrated by dotted lines and arrows.

Referring to FIG. 5(B), and FIGS. 6(A), 6(B) and 6(D), heat generated infourth conductor pattern 85B is transferred onto fourth conductorpattern 85B and transferred from fourth conductor pattern 85B throughelectric insulating layer 82A to third conductor pattern 85A and thermalconductive members 91A to 91C formed at a position overlapping fourthconductor pattern 85B when viewed from the orthogonal direction. Heattransferred to third conductor pattern 85A and thermal conductivemembers 91A to 91C is transferred together with heat generated in thirdconductor pattern 85A from vias 81E, 81G to 81J to casing 71 throughfirst conductor pattern 85D and conductor patterns 86D, 87D.Furthermore, heat transferred to third conductor pattern 85A and thermalconductive members 91A to 91C is transferred to conductor patterns 86B,88B through electric insulating layer 82A and transferred from vias 81E,81G to 81J to casing 71 through first conductor pattern 85D andconductor patterns 86D, 87D. The larger the area in which fourthconductor pattern 85B and third conductor pattern 85A overlap each otherin the orthogonal direction, the more effectively the heat transfer isperformed through electric insulating layer 82A.

Referring to FIG. 5(C), and FIGS. 6(A), 6(B) and 6(D), heat generated insecond conductor pattern 85C is transferred onto second conductorpattern 85C and transferred from second conductor pattern 85C throughelectric insulating layer 82C to first conductor pattern 85D and thermalconductive members 91D to 91F formed at a position overlapping secondconductor pattern 85C when viewed from the orthogonal direction. Heattransferred to first conductor pattern 85D and thermal conductivemembers 91D to 91F is transferred together with heat generated in firstconductor pattern 85D to casing 71. The larger the area in which secondconductor pattern 85C and first conductor pattern 85D overlap each otherin the orthogonal direction, the more effectively the heat transfer isperformed through electric insulating layer 82C.

<Operation Effects>

Isolated converter 100 has first surface 8A and second surface 8Dpositioned on the opposite side to first surface 8A and includesmultilayer substrate 8 having first through hole 84C extending fromfirst surface 8A to second surface 8D and magnetic core 13 partiallypassing through first through hole 84C. Multilayer substrate 8 includesthird conductor pattern 85A formed on first surface 8A in the form ofwinding on the periphery of first through hole 84C, first conductorpattern 85D formed on second surface 8D in the form of winding on theperiphery of first through hole 84C, fourth conductor pattern 85B formedbetween first surface 8A and second surface 8D in the form of winding onthe periphery of first through hole 84C and formed at a positionoverlapping third conductor pattern 85A when viewed from a directionorthogonal to first surface 8A, at least one thermal conductive members91A to 91F formed on at least one of third conductor pattern 85A andfirst conductor pattern 85D and having a portion disposed betweenmultilayer substrate 8 and magnetic core 13, and electric insulatinglayers 82A, 82C (insulative heat-transferring members) electricallyinsulating third conductor pattern 85A and first conductor pattern 85Dfrom fourth conductor pattern 85B. Third conductor pattern 85A and firstconductor pattern 85D are electrically connected with each other.

Isolated converter 100 in this manner includes electric insulatinglayers 82A, 82C electrically insulating third conductor pattern 85A andfirst conductor pattern 85D from fourth conductor pattern 85B, so thatfourth conductor pattern 85B can be configured as a primary-side coiland third conductor pattern 85A and first conductor pattern 85D can beconfigured as secondary-side coils. Then, fourth conductor pattern 85Bis formed at a position overlapping third conductor pattern 85A, so thatisolated converter 100 can be reduced in size compared with aconventional isolated converter in which the primary-side coil and thesecondary-side coil are formed side by side on a first surface.

In isolated converter 100, since fourth conductor pattern 85B ispositioned at a position overlapping third conductor pattern 85A, heatgenerated in fourth conductor pattern 85B is transferred to thirdconductor pattern 85A through electric insulating layer 82A.Furthermore, in isolated converter 100, since thermal conductive members91A to 91C are formed on third conductor pattern 85A, heat generated inthird conductor pattern 85A and heat transferred to third conductorpattern 85A can be transferred in a direction along first surface 8A. Asa result, formation of a large temperature difference between thirdconductor pattern 85A and fourth conductor pattern 85B that are coilpatterns can be suppressed. Therefore, isolated converter 100 can havehigh heat dissipation characteristic because of third conductor pattern85A incorporated in a heat dissipation path. If a large temperaturedifference is formed on a coil pattern, it is necessary to form a viafor heat transfer to serve as a heat dissipation path near the portionin the coil pattern where heat is likely to be relatively high. When thevia for heat transfer is formed for the primary-side coil and thesecondary-side coil formed to overlap in the orthogonal direction, itneed to be formed at an isolation distance from at least one of thecoils. In this case, it is difficult to reduce the size of thetransformer because of the isolation distance. By contrast, isolatedconverter 100 has a high heat dissipation characteristic without forminga via for heat transfer near third conductor pattern 85A and fourthconductor pattern 85B and therefore can be further reduced in sizecompared with an isolated converter in which the primary-side coil andthe secondary-side coil are formed so as to overlap each other and a viafor heat transfer is formed near these coils.

In isolated converter 100 described above, multilayer substrate 8further includes second conductor pattern 85C formed between firstsurface 8A and second surface 8D in the form of winding on the peripheryof first through hole 84C and having a portion formed at a positionoverlapping at least one of third conductor pattern 85A and firstconductor pattern 85D when viewed from the orthogonal direction. Thirdconductor pattern 85A, fourth conductor pattern 85B, second conductorpattern 85C, and first conductor pattern 85D are formed in order in theorthogonal direction. Fourth conductor pattern 85B and second conductorpattern 85C are electrically connected with each other. The distancebetween third conductor pattern 85A and fourth conductor pattern 85B inthe orthogonal direction and the distance between first conductorpattern 85D and second conductor pattern 85C in the orthogonal directionare shorter than the distance between fourth conductor pattern 85B andsecond conductor pattern 85C in the orthogonal direction. That is, thethickness of electric insulating layers 82A, 82C is smaller than thethickness of electric insulating layer 82B.

In this manner, a plurality of coil patterns can be formed between firstsurface 8A and second surface 8D of multilayer substrate 8, so that, forexample, the turns of primary-side coil 11A (or secondary-side coil)formed with fourth conductor pattern 85B and second conductor pattern85C can be readily increased. Furthermore, since the thickness ofelectric insulating layers 82A, 82C is smaller than the thickness ofelectric insulating layer 82B, heat conduction from fourth conductorpattern 85B to third conductor pattern 85A through electric insulatinglayer 82A and heat conduction from second conductor pattern 85C to firstconductor pattern 85D through electric insulating layer 82C can beefficiently performed.

When electric insulating layer 82B is formed to be thick, parasiticcapacitor produced between fourth conductor pattern 85B in the form ofwinding formed on conductor pattern layer 81B and second conductorpattern 85C in the form of winding formed on conductor pattern layer 81Ccan be reduced. Therefore, in isolated converter 100, vibration duringthe on/off operation of a switching element, which may cause noise, canalso be suppressed.

Isolated converter 100 described above further includes casing 71connected to at least part of first conductor pattern 85D. By doing so,first conductor pattern 85D and third conductor pattern 85A electricallyconnected to first conductor pattern 85D can be incorporated into a heatdissipation path extending from fourth conductor pattern 85B to casing71. Isolated converter 100 thus has a high heat dissipationcharacteristic because formation of a large temperature difference issuppressed in third conductor pattern 85A.

In isolated converter 100 described above, multilayer substrate 8further includes fifth conductor pattern 86D formed in a region onsecond surface 8D that at least partially overlaps third conductorpattern 85A but does not overlap first conductor pattern 85D and fourthconductor pattern 85B when viewed from the orthogonal direction, and via81G formed so as to extend from first surface 8A to second surface 8Dand connecting third conductor pattern 85A with fifth conductor pattern86D. At least part of fifth conductor pattern 86D is connected to casing71.

In this manner, in addition to the heat dissipation path from thirdconductor pattern 85A to casing 71 through first conductor pattern 85D,a heat dissipation path from third conductor pattern 85A to casing 71through fifth conductor pattern 86D can be formed. Therefore, isolatedconverter 100 having such a configuration has an even higher heatdissipation characteristic, compared with isolated converter 100 onlyhaving a heat dissipation path from third conductor pattern 85A tocasing 71 through first conductor pattern 85D.

In isolated converter 100 described above, multilayer substrate 8further includes sixth conductor patterns 86B, 86C formed between firstsurface 8A and second surface 8D and having a portion formed at aposition overlapping at least one of third conductor pattern 85A andfirst conductor pattern 85D when viewed from the orthogonal direction.Fourth conductor pattern 85B is electrically insulated from sixthconductor patterns 86B, 86C. Sixth conductor patterns 86B, 86C areconnected to casing 71.

In this manner, in addition to the heat dissipation path from thirdconductor pattern 85A to casing 71 through first conductor pattern 85D,a heat dissipation path from third conductor pattern 85A to casing 71through sixth conductor patterns 86B, 86C can be additionally formed.Therefore, isolated converter 100 having such a configuration has aneven higher heat dissipation characteristic, compared with isolatedconverter 100 only having a heat dissipation path from third conductorpattern 85A to casing 71 through first conductor pattern 85D.

<Modification>

In isolated converter 100, the thermal conductive member that may beformed on third conductor pattern 85A and first conductor pattern 85D ofmultilayer substrate 8 is not limited to the configuration shown in FIG.5 and FIG. 6.

As shown in FIG. 7(A), two thermal conductive members 91G, 91H eachhaving an L-shaped two-dimensional shape may be formed at a distancefrom each other on third conductor pattern 85A. As shown in FIG. 7(B),one thermal conductive member 91J having a C-shaped two-dimensionalshape may be formed on third conductor pattern 85A.

As shown in FIGS. 8(A) and 8(B), a thermal conductive member 91K may beformed so as to overlap vias 81G, 81H when viewed from the orthogonaldirection and connected to vias 81G, 81H. Thermal conductive member 91Kmay be connected, for example, onto third conductor pattern 85A byreflow soldering. In this case, the amount of solder is slightlyincreased so that the inside of vias 81G, 81H can be filled with solderduring heating for reflow. Thus, the solder fills in the copper platingformed on the interior walls of vias 81G, 81H and therefore the soldercan serve as a heat transfer path in addition to copper plating. As aresult, the heat dissipation characteristic through vias 81G, 81H can beincreased. Although FIG. 7 and FIG. 8 show the thermal conductivemembers on third conductor pattern 85A, the thermal conductive membersformed on first conductor pattern 85D may have a similar configuration.

As described above, via 81F connecting fourth conductor pattern 85B withsecond conductor pattern 85C may be formed to reach second surface 8D.In this case, as shown in FIG. 9, in fourth conductor pattern 85B andsecond conductor pattern 85C, the width of the portion connected to via81F (the length in a direction vertical to the extending direction offourth conductor pattern 85B and second conductor pattern 85C) may berelatively smaller than the other portion. Also in this manner, arelatively narrow portion is connected to via 81F and therefore has ahigh heat dissipation characteristic. A relatively wide portion ispositioned at a distance from the narrow portion connected to via 81Fbut has a relatively large area, which enables effective heatdissipation to third conductor pattern 85A or first conductor pattern85D through electric insulating layers 82A, 82C (see FIG. 3).

Second Embodiment

Referring now to FIG. 10 to FIG. 12, an isolated converter according toa second embodiment will be described. The isolated converter accordingto the second embodiment basically has a similar configuration asisolated converter 100 according to the first embodiment but differs inthe secondary-side circuit configuration and the configuration ofconductor patterns on multilayer substrate 8 forming the secondary-sidecircuit.

As shown in FIG. 10, the anode terminals of rectifying elements 31C, 31Dforming rectifying circuit 8 are connected to secondary-side coils 12A,12B of transformer 1. The cathode terminals of rectifying elements 31C,31D are connected to smoothing circuit 4 (contact point 44).

As shown in FIG. 11, one end of third conductor pattern 85A is connectedto the anode terminal of rectifying element 31C. The other end of thirdconductor pattern 85A has a fixing hole 73C. Fixing hole 73C has aconfiguration similar to fixing holes 73A, 73B and is formed to extendfrom first surface 8A to second surface 8D and pass through conductorpattern layers 81A to 81D. On the inner circumferential surface offixing hole 73C, a conductive film of a material having electricalconductivity, for example, a Cu film may be formed. The conductive filmmay be formed, for example, by plating. The other end of third conductorpattern 85A is connected to first conductor pattern 85D and casing 71through fixing hole 73C. The anode terminal of rectifying element 31D isconnected to conductor pattern 86 formed at an isolation distance fromthird conductor pattern 85A.

The cathode terminals of rectifying elements 31C, 31D are connected toconductor pattern 89A formed at an isolation distance from thirdconductor pattern 85A on conductor pattern layer 81A. Conductor pattern89A forms contact point 44.

Conductor pattern layers 81B, 81C, 81D have conductor patterns 89B, 89C,89D, respectively, formed at an isolation distance from fourth conductorpattern 85B, second conductor pattern 85C, and first conductor pattern85D. Conductor patterns 89A to 89D are connected through via 81K andfurther connected to casing 71 with heat dissipation sheet 72interposed.

As shown in FIGS. 11(A) and 11(D), thermal conductive members 91L, 91M,91N are formed on third conductor pattern 85A. Thermal conductivemembers 91P, 91Q, 91R are formed on first conductor pattern 85D. Thermalconductive members 91L to 91R basically have a similar configuration asthermal conductive members 91A to 91F but differ in that the gap portionbetween the thermal conductive members formed on third conductor pattern85A is formed so as to overlap the thermal conductive member formed onfirst conductor pattern 85D.

The gap portion between thermal conductive member 91L and thermalconductive member 91M is formed so as to overlap thermal conductivemember 91Q when viewed from the orthogonal direction. The gap portionbetween thermal conductive member 91L and thermal conductive member 91Nis formed so as to overlap thermal conductive member 91P when viewedfrom the orthogonal direction. Similarly, when viewed from theorthogonal direction, the gap portion between thermal conductive member91P and thermal conductive member 91Q is formed so as to overlap thermalconductive member 91L, and the gap portion between thermal conductivemember 91P and thermal conductive member 91R is formed so as to overlapthermal conductive member 91N.

The heat dissipation paths in the isolated converter according to thesecond embodiment are basically similar to the heat dissipation paths inisolated converter 100 according to the first embodiment. That is,fourth conductor pattern 85B is formed at a position overlapping thirdconductor pattern 85A, so that heat generated in fourth conductorpattern 85B can be transferred to third conductor pattern 85A throughelectric insulating layer 82A. Furthermore, thermal conductive members91L to 91N are formed on third conductor pattern 85A, so that heatgenerated in third conductor pattern 85A and heat transferred to thirdconductor pattern 85A can be transferred in a direction along firstsurface 8A.

The isolated converter according to the second embodiment thereforeachieves the similar effect as in isolated converter 100 according tothe first embodiment.

On the other hand, in the case where the gap portion between thermalconductive member 91L and thermal conductive member 91M is formed so asto overlap the gap portion between thermal conductive member 91L andthermal conductive member 91M when viewed from the orthogonal directionas in isolated converter 100 according to the first embodiment, warpageoriginating from the gap portion may occur in multilayer substrate 8.When warpage occurs in multilayer substrate 8, multilayer substrate 8may be damaged depending on the amount of warpage. When warpage occursin multilayer substrate 8, depending on the amount of warpage, thethickness of heat dissipation sheet 72 connecting multilayer substrate 8with casing 71 need be increased by the amount of warpage of multilayersubstrate 8, possibly resulting in reduction of the heat dissipationcharacteristic of isolated converter 100. Such a problem may beaddressed, for example, by increasing the thickness of multilayersubstrate 8 to increase its rigidity and suppressing increase of theamount of warpage of multilayer substrate 8.

By contrast, in the isolated converter according to the secondembodiment, the gap portion between thermal conductive member 91L andthermal conductive member 91M is formed to overlap thermal conductivemember 91Q when viewed from the orthogonal direction, so that thewarpage of multilayer substrate 8 originating from the gap portionbetween thermal conductive member 91L and thermal conductive member 91Mcan be suppressed by thermal conductive member 91Q. As a result, theisolated converter according to the second embodiment has a high heatdissipation characteristic similar to isolated converter 100 accordingto the first embodiment while the thickness of multilayer substrate 8can be reduced compared with isolated converter 100.

In the isolated converter according to the second embodiment, one end ofeach of third conductor pattern 85A and first conductor pattern 85D hasthe same potential as casing 71 and therefore is directly connected tocasing 71 through fixing hole 73C. Therefore, in the isolated converteraccording to the second embodiment, the heat dissipation characteristicof the heat dissipation path through third conductor pattern 85A andfirst conductor pattern 85D is increased, compared with isolatedconverter 100 connected to casing 71 with heat dissipation sheet 72interposed.

Third Embodiment

Referring now to FIG. 13 to FIG. 15, an isolated converter according toa third embodiment will be described. The isolated converter accordingto the third embodiment basically has a similar configuration asisolated converter 100 according to the first embodiment but differs inthe primary-side and secondary-side circuit configuration and theconfiguration of conductor patterns forming circuits on multilayersubstrate 8.

In the isolated converter according to the third embodiment,primary-side coils 11B, 11C of transformer 1 are configured with a thirdconductor pattern 85E formed on conductor pattern layer 81A and a firstconductor pattern 85H formed on conductor pattern layer 81D. Asecondary-side coil 12C of transformer 1 is configured with a fourthconductor pattern 85F formed on conductor pattern layer 81B and a secondconductor pattern 85G formed on conductor pattern layer 81C. Thirdconductor pattern 85E, first conductor pattern 85H, fourth conductorpattern 85F, and second conductor pattern 85G are formed in the form ofwinding so as to surround fixing hole 74C.

As shown in FIG. 13, primary-side drive circuit 2 includes switchingelements 21E, 21F. The drain terminals of switching elements 21E, 21Fare connected to the corresponding ends of primary-side coils 11B, 11Cof transformer 1. The source terminals of switching elements 21E, 21Fare connected to the negative side (reference potential 7) of a DC powersupply with an input voltage Vin. A contact point 27 betweenprimary-side coils 11B and 11C of transformer 1 is connected to thepositive side of the DC power supply.

As shown in FIG. 13, rectifying circuit 3 is configured with rectifyingelements 31E, 31F connected in series and rectifying elements 31G, 31Hconnected in series. A secondary-side coil 12C of transformer 1 isconnected between a contact point 35 between rectifying element 31E andrectifying element 31F and a contact point 36 between rectifying element31G and rectifying element 31H. The cathode terminals of rectifyingelements 31E, 31G are connected to smoothing coil 42. The anodeterminals of rectifying elements 31E, 31G are connected to the negativeside of smoothing capacitor 41.

As show in FIGS. 14(A) and 14(D), a conductor pattern layer 81A formedon first surface 8A of multilayer substrate 8 has a third conductorpattern 85E forming primary-side coil 11C and a conductor pattern 90Aformed adjacent to the corner portion of third conductor pattern 85E atan isolation distance therefrom. Conductor pattern 90A is connected tocasing 71 through fixing hole 73C. In other words, conductor patternlayer 81A has conductor pattern 90A connected to casing 71 and has thirdconductor pattern 85E formed at an isolation distance from conductorpattern 90A and formed so as to have an area as large as possible.

A conductor pattern layer 81D formed on second surface 8D of multilayersubstrate 8 has a first conductor pattern 85H forming primary-side coil11B. Conductor pattern layers 81B and 81C formed between first surface8A and second surface 8D have a fourth conductor pattern 85F and asecond conductor pattern 85G, respectively, to form secondary-side coil11C.

Multilayer substrate 8 has fixing holes 73D, 73E, 73F, 73G. Fixing holes73D to 73G basically have a similar configuration as fixing holes 73A,73B. Fixing holes 73D to 73G are connected to the conductor patternsformed on conductor pattern layers 81A to 81D and are connected tocasing 71. Fixing holes 73D, 73E are connected to conductor pattern 90Aformed adjacent to the corner portion of third conductor pattern 85E atan isolation distance therefrom, conductor pattern 90B formed adjacentto fourth conductor pattern 85F at an isolation distance therefrom,conductor pattern 90C formed adjacent to second conductor pattern 85G atan isolation distance therefrom, and conductor pattern 90D formedadjacent to the corner portion of first conductor pattern 85H at anisolation distance therefrom. Conductor patterns 90B, 90C are formedbetween first surface 8A and second surface 8D and formed as sixthconductor patterns having a portion formed at a position overlapping atleast one of third conductor pattern 85E and first conductor pattern 85Hwhen viewed from the orthogonal direction.

One end of third conductor pattern 85E is connected to the drainterminal of switching element 21F and is connected to via 81L. The otherend of third conductor pattern 85E is connected to via 81L and contactpoint 27. The source terminals of switching elements 21E, 21F areconnected to casing 71 (reference potential 7), for example, throughfixing holes 73F, 73G. One end of first conductor pattern 85H isconnected to the drain terminal of switching element 21E through via81N. The other end of first conductor pattern 85H is connected to via81L and contact point 27. One end of fourth conductor pattern 85F isconnected to contact point 35 of rectifying circuit 3. One end of secondconductor pattern 85G is connected to contact point 36 of rectifyingcircuit 3. The other end of fourth conductor pattern 85F is connected tothe other end of second conductor pattern 85G through via 81F.

As shown in FIGS. 14(A) and 14(D), thermal conductive members 91S, 91T,91U are formed on third conductor pattern 85E. Thermal conductivemembers 91V, 91W, 91X are formed on first conductor pattern 85H. Thermalconductive members 91S to 91X basically have a similar configuration asthermal conductive members 91A to 91F. Thermal conductive members 91T,91U, 91W, 91X are formed at a portion adjacent to conductor pattern 90Aat an isolation distance therefrom in third conductor pattern 85E orfirst conductor pattern 85H. Thermal conductive members 91T, 91U, 91W,91X have a convex two-dimensional shape.

A plurality of conductor patterns 86B formed at an isolation distancefrom fourth conductor pattern 85F are connected to fixing holes 73D, 73Eand vias 81L, 81M, 81N. A plurality of conductor patterns 86C formed atan isolation distance from second conductor pattern 85G are connected tofixing holes 73D, 73E and vias 81L, 81M, 81N.

Conductor patterns 86B, 86C connected to fixing holes 73D, 73E areformed so as to overlap third conductor pattern 85E and first conductorpattern 85H when viewed from the orthogonal direction.

The heat dissipation paths in the isolated converter according to thethird embodiment are basically similar to the heat dissipation paths inisolated converter 100 according to the first embodiment. Heat generatedin fourth conductor pattern 85F is transferred to third conductorpattern 85E through electric insulating layer 82A and spread togetherwith heat generated in third conductor pattern 85E over thermalconductive members 91S to 91U and then transferred to casing 71 throughvias 81L to 81N and heat dissipation sheet 72. Heat generated in thirdconductor pattern 85E and heat transferred from fourth conductor pattern85F to third conductor pattern 85E are spread over thermal conductivemembers 91S to 91U and then transferred to conductor pattern 86B throughelectric insulating layer 82A and transferred to casing 71 throughfixing holes 73D, 73E and fixtures 74D, 74E (for example, screws).Similarly, heat generated in second conductor pattern 85G is transferredto first conductor pattern 85H through electric insulating layer 82C andspread together with heat generated in first conductor pattern 85H overthermal conductive members 91V to 91X, and then transferred to casing 71through heat dissipation sheet 72. Heat generated in second conductorpattern 85G is transferred to conductor pattern 86D through electricinsulating layer 82C and transferred to casing 71 through fixing holes73C, 73D.

That is, since fourth conductor pattern 85F is formed at a positionoverlapping third conductor pattern 85E, heat generated in fourthconductor pattern 85F may be transferred to third conductor pattern 85Ethrough electric insulating layer 82A. Furthermore, since thermalconductive members 91S to 91U are formed on third conductor pattern 85E,heat generated in third conductor pattern 85E and heat transferred tothird conductor pattern 85E can be transferred in a direction alongfirst surface 8A.

The isolated converter according to the third embodiment thus canachieve the similar effect as in isolated converter 100 according to thefirst embodiment. In the isolated converter according to the thirdembodiment, conductor patterns 90A, 90B directly connected to casing 71through fixing holes 73D, 73E are formed near third conductor pattern85E, the corner portion of second conductor pattern 85G, or firstconductor pattern 85H, fourth conductor pattern 85F, configured as aprimary-side coil or a secondary-side coil.

Therefore, in the isolated converter according to the third embodiment,the heat dissipation characteristic of the heat dissipation path throughthird conductor pattern 85A and first conductor pattern 85D isincreased, compared with isolated converter 100.

In the isolated converter according to the first to third embodiments,the turns of the primary-side coil or the secondary-side coil may be anynumber depending on the step-up ratio or the step-down ratio. Forexample, in isolated converter 100 according to the first embodimentshown in FIG. 4 and FIG. 5, given that the number of turns ofprimary-side coil 11A is six and the number of turns of secondary-sidecoils 12A, 12B is one, transformer 1 has a step-down ratio of 6:1.

Fourth Embodiment.

In the isolated converter according to the first to third embodiments,primary-side coil 11A is formed with fourth conductor pattern 85B andsecond conductor pattern 85C. However, embodiments are not limited tothis configuration. As shown in FIG. 16, primary-side coil 11A may beformed only with second conductor pattern 85C.

In conductor pattern layer 81B, a seventh conductor pattern 92B isformed in place of fourth conductor pattern 85B. When viewed from theorthogonal direction, seventh conductor pattern 92B is formed at aposition overlapping third conductor pattern 85A, second conductorpattern 85C, and first conductor pattern 85D. One end of seventhconductor pattern 92B is connected through via 81F and to one end ofsecond conductor pattern 85C. The other end of seventh conductor pattern92B is connected to contact point 22 of primary-side drive circuit 2.

As shown in FIG. 16(b), sixth conductor patterns 86B may be formedwidely in a region not having seventh conductor pattern 92B andconductor patterns 87B, 88B on conductor pattern layer 81B. The totalarea of sixth conductor patterns 86B in the conductor pattern 81B layerin the fourth embodiment may be larger than, for example, the total areaof sixth conductor patterns 86B in the conductor pattern 81B layer inthe first to third embodiments. A plurality of sixth conductor patterns86B, seventh conductor pattern 92B, and conductor patterns 87B, 88B areformed at an isolation distance from each other. Since current isprevented from flowing between through hole 84C and through hole 84A andbetween through hole 84C and through hole 84B, the transformer canoperate normally in the isolated converter.

Second conductor pattern 85C is formed as a primary-side coil, and thirdconductor pattern 85A and first conductor pattern 85D are formed assecondary-side coils. Therefore, the isolated converter according to thefourth embodiment can be reduced in size compared with a conventionalisolated converter in which the primary-side coil and the secondary-sidecoil are formed side by side on a first surface.

Since seventh conductor pattern 92B is formed at a position overlappingthird conductor pattern 85A, heat generated in seventh conductor pattern92B may be transferred to third conductor pattern 85A through electricinsulating layer 82A. The isolated converter according to the fourthembodiment thus can achieve the similar effect as in isolated converter100 according to the first embodiment.

Fifth Embodiment

Referring now to FIG. 17 and FIG. 18, an isolated converter according toa fifth embodiment will be described. The isolated converter accordingto the fifth embodiment basically has a similar configuration asisolated converter 100 according to the first embodiment but differs inthe primary-side and secondary-side circuit configuration and theconfiguration of the conductor patterns forming circuits on multilayersubstrate 8.

In the isolated converter according to the fifth embodiment, aprimary-side coil 11D of transformer 1 is configured with secondconductor pattern 85C formed on conductor pattern layer 81C. Asecondary-side coil 12D of transformer 1 is configured with firstconductor pattern 85D formed on conductor pattern layer 81D. Each offirst conductor pattern 85D and second conductor pattern 85C is formedin the form of winding so as to surround through hole 84C.

As shown in FIG. 17, primary-side drive circuit 2 is configured with aswitching element 21A and a switching element 21B connected in seriesand a switching element 21C and a switching element 21D connected inseries. A primary-side coil 11D of transformer 1 is connected between acontact point 22 between switching element 21A and switching element 21Band a contact point 23 between switching element 21C and switchingelement 21D. Switching element 21A and switching elements 21B, 21C, 21Dare, for example, MOSFETs. The drain terminals of switching elements21A, 21C are connected to the positive side of DC power supply 6. Thesource terminals of switching elements 21B, 21D are connected to thenegative side of DC power supply 6.

Rectifying circuit 3 is configured with rectifying elements 31E and 31Fconnected in series and rectifying elements 31G and 31H connected inseries. A secondary-side coil 12D of transformer 1 is connected betweena contact point 35 between rectifying element 31E and rectifying element31F and a contact point 36 between rectifying element 31G and rectifyingelement 31H. The cathode terminals of rectifying elements 31E, 31G areconnected to smoothing coil 42. The anode terminals of rectifyingelements 31E, 31G are connected to the negative side of smoothingcapacitor 41.

As shown in FIG. 18(D), a conductor pattern layer 81D formed on secondsurface 8D of multilayer substrate 8 has a first conductor pattern 85Dforming secondary-side coil 12D. As shown in FIG. 18(C), conductorpattern layer 81C formed between first surface 8A and second surface 8Dhas a second conductor pattern 85C forming primary-side coil 11D. Asshown in FIG. 18(B), conductor pattern layer 81B formed between firstsurface 8A and second surface 8D has a seventh conductor pattern 92B. Asshown in FIG. 18(A), conductor pattern layer 81A formed on first surface8A has conductor patterns 93A, 94A.

One end of first conductor pattern 85D is connected to conductor pattern93A on conductor pattern layer 81A through via 81E and is connected tocontact point 35 of rectifying circuit 3 in conductor pattern 93A. Theother end of first conductor pattern 85D is connected to conductorpattern 94A on conductor pattern layer 81A through via 81J and connectedto contact point 36 of rectifying circuit 3 in conductor pattern 94A.

One end of second conductor pattern 85C is connected to seventhconductor pattern 92B on conductor pattern layer 81B through via 81F andconnected to contact point 22 between switching element 21A andswitching element 21B in seventh conductor pattern 92B. The other end ofsecond conductor pattern 85C is connected to contact point 23 betweenswitching element 21C and switching element 21D.

The heat dissipation paths for first conductor pattern 85D and secondconductor pattern 85C are basically similar to those in the first tothird embodiments and will not be further elaborated.

In FIG. 18, switching elements 21A to 21D, rectifying elements 31E to31H, and/or control circuit 5 may be disposed in a portion in which theconductor patterns on conductor pattern layer 81A and conductor patternlayer 81B and via 81F are not shown. Therefore, in the fourthembodiment, the circuits and the components disposed on the periphery ofthe transformer in the first to third embodiments can be disposed tooverlap first conductor pattern 85D and second conductor pattern 85Cthat constitute the transformer. As a result, the isolated converteraccording to the fourth embodiment can be reduced in size compared withthe isolated converter according to the first to third embodiments.

It is noted that no conductor pattern is disposed for connecting throughhole 84C with through hole 84A and connecting through hole 84 withthrough hole 84B. That is, current is prevented from flowing betweenthrough hole 84C and through hole 84A as well as between through hole 84and through hole 84B. The transformer thus can operate normally in theisolated converter.

In the present description, “being formed so as to surround firstthrough hole 84C” is not limited to being formed so as to surround theentire periphery (360 degrees) of through hole 84C but may refer tobeing disposed to the side of through hole 84C at least at the portionoverlapping the coupling portion of the E-shaped core. As used herein“being formed so as to surround first through hole 84C” may refer to,for example, being formed so as to surround three-quarters of theperiphery of through hole 84C. As described above, thermal conductivemembers 91A, 91B, 91C may be formed, for example, in a C shape, forexample, along three sides of through hole 84C having a rectangulartwo-dimensional shape.

In the isolated converter according to the first to fifth embodiments,the magnetic core of transformer 1 may be configured as desired as longas a circulating magnetic path is formed. In the case of E-shaped core13, the cross section vertical to the extending direction of inside leg13C (direction orthogonal to first surface 8A of multilayer substrate 8)is preferably twice or more the cross section vertical to the orthogonaldirection of the outside legs 13A, 13B. The magnetic core of transformer1 may be configured with, for example, two E-shaped cores or may be anEER-shaped core having an E-shaped side surface and having a circularshape in cross section of the inside leg. The magnetic core oftransformer 1 may be provided such that only one magnetic path can beformed. In this case, the magnetic core may be formed with a U-shapedcore having a U shape on the side surface and an I-shaped core or may beformed with two U-shaped cores.

Although embodiments and examples of the present invention have beendescribed above, the foregoing embodiments are susceptible to variousmodifications. It is initially intended that the configurations of theforegoing embodiments and examples are combined as appropriate. Thescope of the present invention is not limited to the foregoingembodiments. The scope of the present invention is shown by the claimsand it is intended that equivalents to the claims and all modificationswithin the scope of the claims are embraced.

REFERENCE SIGNS LIST

1 transformer, 2 primary-side drive circuit, 3 rectifying circuit, 4smoothing circuit, 5 control circuit, 6 DC power supply, 7 referencepotential, 8 multilayer substrate, 8A first surface, 8D second surface,11A, 11B, 11C, 11D primary-side coil, 12A, 12B, 12C, 12D secondary-sidecoil, 13, 14, 43 magnetic core, 21A, 21B, 21C, 21D, 21E, 21F switchingelement, 31A, 31B, 31C, 31D, 31E, 31F, 31G, 31H rectifying element, 41smoothing capacitor, 42 smoothing coil, 73A, 73B, 73C, 73D, 73E, 73F,73G fixing hole, 71 casing, 72 heat dissipation sheet, 74A, 74B, 74D,74E fixture, 84A, 84B, 84C through hole, 81A, 81B, 81C, 81D conductorpattern layer, 81E, 81F, 81G, 81H, 81I, 81J, 81K, 81L, 81M, 81N via,82A, 82B, 82C electric insulating layer, 85A, 85E third conductorpattern, 85B, 85F fourth conductor pattern, 85C, 85G second conductorpattern, 85D, 85H first conductor pattern, 86B, 86C sixth conductorpattern, 86D fifth conductor pattern, 92B seventh conductor pattern,91A, 91B, 91C, 91D, 91E, 91F, 91G, 91H, 91J, 91K, 91L, 91M, 91N, 91P,91Q, 91R, 91S, 91T, 91U, 91V, 91W, 91X thermal conductive member, 100isolated converter.

1. An isolated converter comprising: a multilayer substrate having afirst surface and a second surface positioned on a side opposite to thefirst surface, the multilayer substrate having a first through holeextending from the first surface to the second surface; and a magneticcore partially passing through the first through hole, the multilayersubstrate including a first conductor pattern formed at a positionoverlapping the magnetic core on the second surface when viewed from anorthogonal direction to the first surface, a second conductor patternformed between the first surface and the second surface at a positionoverlapping the magnetic core and the first conductor pattern whenviewed from the orthogonal direction to the first surface, at least onethermal conductive member formed on the first conductor pattern andhaving a portion disposed between the multilayer substrate and themagnetic core, and an insulative heat-transferring member electricallyinsulating the first conductor pattern from the second conductorpattern.
 2. The isolated converter according to claim 1, wherein themultilayer substrate further includes a third conductor pattern formedat a position overlapping the magnetic core on the first surface whenviewed from the orthogonal direction to the first surface, the secondconductor pattern and the third conductor pattern are electricallyinsulated from each other, and the first conductor pattern and the thirdconductor pattern are electrically connected with each other.
 3. Theisolated converter according to claim 2, wherein the multilayersubstrate further includes a fourth conductor pattern formed between thefirst surface and the second surface at a position overlapping themagnetic core and at least one of the first conductor pattern and thethird conductor pattern when viewed from the orthogonal direction, thethird conductor pattern, the fourth conductor pattern, the secondconductor pattern, and the first conductor pattern are formed in orderin the orthogonal direction, the second conductor pattern and the fourthconductor pattern are electrically connected with each other, and adistance in the orthogonal direction between the third conductor patternand the fourth conductor pattern and a distance in the orthogonaldirection between the first conductor pattern and the second conductorpattern are shorter than a distance in the orthogonal direction betweenthe second conductor pattern and the fourth conductor pattern.
 4. Theisolated converter according to claim 1, further comprising a coolerconnected to at least part of the first conductor pattern.
 5. Theisolated converter according to claim 4, wherein a potential of thecooler is a reference potential of a circuit including the firstconductor pattern, and at least part of the first conductor pattern isdirectly connected with the cooler.
 6. The isolated converter accordingto claim 4, wherein the multilayer substrate further includes a fifthconductor pattern formed in a region on the second surface that at leastpartially overlaps the third conductor pattern but does not overlap thefirst conductor pattern and the fourth conductor pattern when viewedfrom the orthogonal direction, and a via formed from the first surfaceto the second surface and connecting the third conductor pattern withthe fifth conductor pattern, and at least part of the fifth conductorpattern is connected to the cooler.
 7. The isolated converter accordingto claim 6, wherein the multilayer substrate further includes a sixthconductor pattern formed between the first surface and the secondsurface and having a portion formed at a position overlapping at leastone of the first conductor pattern and the third conductor pattern whenviewed from the orthogonal direction, the fourth conductor pattern andthe sixth conductor pattern are electrically insulated from each other,and the sixth conductor pattern is connected to the cooler.
 8. Theisolated converter according to claim 1, wherein the multilayersubstrate further includes a plurality of the thermal conductivemembers, the thermal conductive members include a plurality of firstthermal conductive members formed spaced apart from each other by a gapportion on one of the first surface and the second surface, and a secondthermal conductive member formed on the other of the first surface andthe second surface, and the gap portion between the first thermalconductive members is formed so as to overlap the second thermalconductive member when viewed from the orthogonal direction.
 9. Theisolated converter according to claim 5, wherein the multilayersubstrate further includes a fifth conductor pattern formed in a regionon the second surface that at least partially overlaps the thirdconductor pattern but does not overlap the first conductor pattern andthe fourth conductor pattern when viewed from the orthogonal direction,and a via formed from the first surface to the second surface andconnecting the third conductor pattern with the fifth conductor pattern,and at least part of the fifth conductor pattern is connected to thecooler.
 10. The isolated converter according to claim 9, wherein themultilayer substrate further includes a sixth conductor pattern formedbetween the first surface and the second surface and having a portionformed at a position overlapping at least one of the first conductorpattern and the third conductor pattern when viewed from the orthogonaldirection, the fourth conductor pattern and the sixth conductor patternare electrically insulated from each other, and the sixth conductorpattern is connected to the cooler.
 11. The isolated converter accordingto claim 2, further comprising a cooler connected to at least part ofthe first conductor pattern.
 12. The isolated converter according toclaim 11, wherein a potential of the cooler is a reference potential ofa circuit including the first conductor pattern, and at least part ofthe first conductor pattern is directly connected with the cooler. 13.The isolated converter according to claim 12, wherein the multilayersubstrate further includes a fifth conductor pattern formed in a regionon the second surface that at least partially overlaps the thirdconductor pattern but does not overlap the first conductor pattern andthe fourth conductor pattern when viewed from the orthogonal direction,and a via formed from the first surface to the second surface andconnecting the third conductor pattern with the fifth conductor pattern,and at least part of the fifth conductor pattern is connected to thecooler.
 14. The isolated converter according to claim 13, wherein themultilayer substrate further includes a sixth conductor pattern formedbetween the first surface and the second surface and having a portionformed at a position overlapping at least one of the first conductorpattern and the third conductor pattern when viewed from the orthogonaldirection, the fourth conductor pattern and the sixth conductor patternare electrically insulated from each other, and the sixth conductorpattern is connected to the cooler.
 15. The isolated converter accordingto claim 11, wherein the multilayer substrate further includes a fifthconductor pattern formed in a region on the second surface that at leastpartially overlaps the third conductor pattern but does not overlap thefirst conductor pattern and the fourth conductor pattern when viewedfrom the orthogonal direction, and a via formed from the first surfaceto the second surface and connecting the third conductor pattern withthe fifth conductor pattern, and at least part of the fifth conductorpattern is connected to the cooler.
 16. The isolated converter accordingto claim 15, wherein the multilayer substrate further includes a sixthconductor pattern formed between the first surface and the secondsurface and having a portion formed at a position overlapping at leastone of the first conductor pattern and the third conductor pattern whenviewed from the orthogonal direction, the fourth conductor pattern andthe sixth conductor pattern are electrically insulated from each other,and the sixth conductor pattern is connected to the cooler.
 17. Theisolated converter according to claim 3, further comprising a coolerconnected to at least part of the first conductor pattern.
 18. Theisolated converter according to claim 17, wherein a potential of thecooler is a reference potential of a circuit including the firstconductor pattern, and at least part of the first conductor pattern isdirectly connected with the cooler.
 19. The isolated converter accordingto claim 18, wherein the multilayer substrate further includes a fifthconductor pattern formed in a region on the second surface that at leastpartially overlaps the third conductor pattern but does not overlap thefirst conductor pattern and the fourth conductor pattern when viewedfrom the orthogonal direction, and a via formed from the first surfaceto the second surface and connecting the third conductor pattern withthe fifth conductor pattern, and at least part of the fifth conductorpattern is connected to the cooler.
 20. The isolated converter accordingto claim 19, wherein the multilayer substrate further includes a sixthconductor pattern formed between the first surface and the secondsurface and having a portion formed at a position overlapping at leastone of the first conductor pattern and the third conductor pattern whenviewed from the orthogonal direction, the fourth conductor pattern andthe sixth conductor pattern are electrically insulated from each other,and the sixth conductor pattern is connected to the cooler.